Parking brake mechanism

Abstract

A parking brake mechanism for an air-actuated disc brake includes an electrically powered actuator, an extensible device drivably connected to the electrically powered actuator and able to extend and retract and be held in place in an extended position to thereby apply a brake, and a resilient device arranged to act on the extensible device and maintain a desired level of force to be applied by the parking brake mechanism in the event of contraction of brake components due to cooling.

1 . A parking brake mechanism for an air-actuated disc brake, the parking brake mechanism comprising:
 an electrically powered actuator;   an extensible device drivably connected to the electrically powered actuator and able to extend and retract and be held in place in an extended position to thereby apply a brake; and   a resilient device arranged to act on the extensible device and maintain a desired level of force to be applied by a parking brake mechanism in the event of contraction of brake components due to cooling.   
   
   
       2 . The parking brake mechanism according to  claim 1  wherein the extensible device includes a lead screw arrangement drivable by the electrically powered actuator. 
   
   
       3 . The parking brake mechanism according to  claim 2  wherein the extensible device further includes a latching arrangement. 
   
   
       4 . The parking brake mechanism according to  claim 3  wherein a latched state of the latching arrangement is selectable by driving the electrically powered actuator. 
   
   
       5 . The parking brake mechanism according to  claim 3  wherein the latching arrangement includes multiple axial latching positions. 
   
   
       6 . The parking brake mechanism according to  claim 3  wherein the latching arrangement is of a bayonet-type in which relative rotation of a first component with respect to a second component effects latching. 
   
   
       7 . The parking brake mechanism according to  claim 4  wherein a single actuator may drive the lead screw arrangement and select the latched state. 
   
   
       8 . The parking brake mechanism according to  claim 1  wherein the resilient device is a helical spring. 
   
   
       9 . The parking brake mechanism according to  claim 8  wherein the extensible device is located concentrically within the helical spring. 
   
   
       10 . The parking brake mechanism according to  claim 8  wherein the electrically powered actuator is located within the helical spring. 
   
   
       11 . The parking brake mechanism according to  claim 10  wherein the electrically powered actuator is located concentrically with respect to the helical spring. 
   
   
       12 . The parking brake mechanism according to  claim 8  wherein the electrically powered actuator is located externally of the helical spring. 
   
   
       13 . The parking brake mechanism according to  claim 1  configured to act on a lever portion of a brake operating shaft. 
   
   
       14 . The parking brake mechanism according  claim 1  wherein the parking brake mechanism further includes a service brake actuator. 
   
   
       15 . The parking brake mechanism according to  claim 14  wherein the extensible device is configured to act substantially coaxially with the service brake actuator. 
   
   
       16 . The parking brake mechanism according to  claim 14  wherein the service brake actuator is an air-actuator including a piston or a diaphragm located within an air chamber such that the introduction of pressurized air displaces the piston or the diaphragm to apply the brake. 
   
   
       17 . The parking brake mechanism according to  claim 16  wherein the parking brake mechanism is in fluid flow communication with air chamber such that pressurized air additionally applies a load to compress the resilient device. 
   
   
       18 . The parking brake mechanism according to  claim 16  wherein the extensible device is connected to the piston or the diaphragm such that displacement of the piston or the diaphragm may cause displacement of the extensible device. 
   
   
       19 . The parking brake mechanism according to  claim 18  wherein the extensible device is releasably connected to the piston or the diaphragm such that under certain conditions extensible device may be released therefrom. 
   
   
       20 . A combination service and parking brake actuator comprising:
 a parking brake mechanism for an air-actuated disc brake, the parking brake mechanism including:
 an electrically powered actuator; 
 an extensible device drivably connected to the electrically powered actuator and able to extend and retract and be held in place in an extended position to thereby apply a brake; and 
 a resilient device arranged to act on the extensible device and maintain a desired level of force to be applied by a parking brake mechanism in the event of contraction of brake components due to cooling.